许多μP(微处理器)有内部监视计时器,你可能奇怪为什么还需要另一个独立电路。遗憾的是,更加高度综合的函数都有你想改变的预置参数。而且,内部监视计时器一般是一个触发器和一个计时器的简单结合。如果首次试验程序没有恰当地启动,则计时器没有用。因为程序并未接通监视计时器。监视计时器捕捉的刚好是这个条件。图1的设计使你能置定所有的参数,并完全控制μP的复位。电路包括两串联接入IC_1的单稳电路。IC_(1A)用R_1和C_1控制复位脉冲的宽度,IC_(1B)用R_3和C_3控制脉冲间的间隔。μP应在R_4给监视计时器施加一个窄的负脉冲。如果这个信 Many μP (microprocessor) have internal watchdog timer, you may wonder why you need another separate circuit. Unfortunately, more highly integrated functions have preset parameters that you want to change. Moreover, the internal watchdog timer is generally a simple combination of a trigger and a timer. The timer is not useful if the first trial program did not start properly. Because the program is not connected to watchdog timer. Watch timer capture exactly this condition. The design of Figure 1 allows you to set all the parameters and fully control μP reset. The circuit consists of two monostable circuits connected in series to IC_1. IC_ (1A) controls the reset pulse width with R_1 and C_1, and IC_ (1B) controls the interval between pulses with R_3 and C_3. μP should apply a narrow negative pulse to watchdog timer at R_4. If this letter